Electromagnet



J. HARRIS ELECTROMAGNET July 23, 1929.

Filed Sept. 18, 1924 Inventor Jesse Harris M- W dlttorney.

Patented July 23, 1929.

UNITED STATES PATENT OFFICE.

JESSE HARRIS, OF LA FAYETTE, INDIANA, ASSIGNOR T0 DUNCAN ELECTRIC MANU-FACTURING COMPANY, OF LA FAYETTE,

INDIANA, A CORPORATION OF ILLINOIS.

ELECTROMAGNET.

Application filed September My invention relates to electro-magnets andresides in so constructing and relating the armature as to delay orprevent the opera tion or actuation of the armature load instantly afterthe energization of the ma net. To this end, I construct the armature o?the magnet with two sections in lost motion relation. the magnet pullingupon one armature section and, through the medium of this section, uponthe other section, these armature sections being so related that thefirst section moves before moving the second. The two sections of thearmature desirably thereafter move together to jointly operate oractuate the armature load which is coupled with the second armaturesection that is the later to move.

The magnet of my invention is of particular service when employed tooperate a circuit breaker. It frequently happens that a surge of currentflows over a line that does no ma .crial damage, be 'ause of itsextremely short duration, although it may be of a high value. If thebreaker should open. on such short time overloads, it would add anincreased burden to the maintenance of the service, necessitatingfrequent resetting of the circuit breaker. If the operating magnet ofthe circuit breaker is constructed in accordance with my invention, apredetermined interval of time may intervene before the lucakcr operatesto enable the surges calculated for to subside.

The accompanying drawing illustrates the employment of the preferredform of magnet of my invention as the operating magnet of a circuitbreaker, a circuit to which the breaker may be applied beingdiagrammatically illustrated.

The circuit illustrated includes a generator of alternating current 1,to which the inven tion is not to be limited, however. Current suppliedfrom the generator to the load 2 by way of the mains 3, 4. The circuitbreaker switch is included in the main 3, this switch having twometallic complemental contacts, one in the form of a contact block 5 andthe other in the form of a switch arm 6, composed of a plurality ofcurved spring blades. The circuit breaker operating electro-magnet 7 hasits winding serially included in the main 3. The armature of thismagnet, later to be fully described, is in loose connection with one endof a link 8 Whose other end is connect 18, 1924. Serial No. 738,513.

ed with a toggle link 9 which is pivoted upon a bracket 10. A secondtoggle link 11 connects the link 9 with the switch arm 6. A hand lever12 is fixed upon the link 9 on the other side of its pivot therefrom.The switch is closed by the handle and is automatically opened whenexcessive current flows in the circuit for a sufficient length of time,this excessive current increasing the energization of the magnet tocause the magnet ar mature to operate upon the link 8 which, in turn,operates upon the toggle link 9 to break the toggle and open the switch.

The magnet of my invention, as it is preferably constructed, has itswinding disposed about the closed or imperforate hollow cylinder orcasing 13 which is preferably made of non-magnetic material, such asbrass. The armature is composed of two sections, the section 14 being inthe form of a floating iron core which is contained within the interiorof the casing 13 and is movable longitudinally thereof. The motion ofthis armature section is mechanically retarded as by means of the oil 15which, together with said armature section, substantially fills theinterior of said casing. The thickness of the oil and the clearancebetween the core and the casing delay the movement of the core, whichwith its casing constitutes one form of dash pot. The remaining section16 of the armature is an iron bar pivoted between its ends upon thelower end of the bracket 10, the link 8 passing through this armaturesection and having av head 17 which is engaged by the armature section16, when the armature is attracted, to open the circuit breaker switch.The urinature section 16 has an elliptical hole 18 through which thelower end of the casing projects. The core 14 normally projects be lowthe bottom face of armature section 16 to such an extent as to permitthe core 14 to be moved upwardly alone an appreciable distance beforethe flux will cause the armature section 16 and the armature section 1-1to thereafter move upwardly together. The bottom of the casing 13constitutes a support or abutment holding the armature section 14: inposition to be moved part way alone, that is, without initially movingthe armature section 16, when the magnet is energized. An appreciableperiod intervenes between the energi'zjat-ion of the magnet and themovement of the load operating section 16 of the 311113 ture, the lengthof the period being determined by the design of the instrument and thecharacter of overload.

From the description hitherto given it will be understood that thearmature section 1'-l responds before the armature section 16. lhis isdue to the fact that the armature section 16 is outside of the range ofthe mag net coil, directly, the field established by the magnet coilacting upon the armature section 16 through the inermediation of thearmature section 14, the dash pot 13 bei g of nonmagnetic material. Itwill also be observed that the armature section 1% passes through theplane of the armature section 16, when the magnet is deenergized, andprojects below the armature section 16 as well above it. hen the magnetis initially energized the magnetic flux generated by the magnet windingoperates, in part, to lift the armature section 1 1, a portion of thisfiux passing through the armature section 1 1 and straying from thebottom thereof to draw downwardly upon the armature section 16 to overcome any tendency on the part of the armature section 15L to instantlydraw the armature section 16 upwardly when the section 14: responds tothe magnetic pull of the mag net. When the magnet is deenergized and thearmature is unattracted, the armature section 14 has a portion in thespace between the energizing portion of the magnet and the armaturesection .16 so that when the magnet is energized, the armature section14 will be initially materially subject to greater pull that thearmature section 16.

Changes may be made without departing from my invention.

Having thus described my invention, 1 claim 1. An electro-magnetincluding the winding thereof;a casing of non-magnetic material aboutwhich said winding is disposed and having one end projecting beyond oneend of the winding, the hollow interior of the casing being alsosurrounded by the winding and extending, with the aforesaid casing end,beyond the aforesaid end of the winding; and an armature formed in twoindividually and relatively movable sections, one of whicn is containedwithin the aforesaid casing and is movable along the axis of the windingwithin and with respect to the casing and which is constrained to haveits outer end in proximity to the aforesaid projecting end of the casingwhen the magnet is deenergized, the inner end of this armature sectionbeing within the range of the magetic field due to the magnet windingwhen the magnet is energized, the other armature section being upon theexterior of the aforesaid casing that extends outwardly from the windingbeyond this armature section and being positioned to be further from theinfluence of the winding than the first armaturesection when the magnetis initially energized, the first armature section extending away fromthe winding beyond the sec ond armature section when the magnet isdeenergized to enable the first armature section to be moved throughouta part of its range of movement without appreciably moving the secondarmature section when the magnet is initially energized and to enablethe first armature section in completing its movement to move the secondarmature section upon continued energization of the magnet.

2. The structure of claim 1 wherein a motion retarding fiuid is alsocontained within the casing and of sufiicient quantitv to retard themovement of the armature section that is within this casing.

In witness whereof, I hereunto subscribe my name. i JESSE IARRIS.

